A mobile communication system has developed in order to provide a voice service while ensuring user activity. The mobile communication system has gradually extended to a data service in addition to the voice service and has currently developed to the extent of providing a high-speed data service. However, in a mobile communication system which currently provides a service, an improved mobile communication system has been required due to resource lack or user demand for higher-speed service.
One of most important requirements of a next-generation radio access system is to support requirement of a data transfer rate. In order to support requirement of a data transfer rate, various techniques such as multiple input multiple output (MIMO), cooperative multipoint transmission (CoMP), carrier aggregation (CA)/multiple cells, relay, etc. have been studied.
Such techniques have a difficulty in equally utilizing a downlink control channel used in an existing system, in order to obtain maximum performance. In a 3GPP LTE-A system, an enhanced physical downlink control channel (e-PDCCH) has been introduced in order to increase capacity of a PDCCH in an existing 3GPP LTE system.